Mating period and gametogenesis of a temperate population of Gekko japonicus were investigated by gross dissection and histology. The mating period of this gecko extended throughout the active season, as inferred from the year-round presence of sperm in the epididymis, consistent with reports of copulation. Because oogenesis occurred from April through July, the oogenetic pattern followed an associated reproductive cycle typical of temperate areas. However, although males exhibited an associated reproductive cycle, spermiogenesis continued throughout the active season, similar to that of constant reproductive cycles observed in the tropical lizards.